Gossip Girl's Kaylee DeFer Welcomes Baby Boy Theodore!

The 26-year-old Gossip Girl actress gave birth to her baby on Friday (September 20) at 10:14pm. He weighed in at 8 pounds and 13 ounces.

“Kaylee was a rock star!” Michael, 43, said of the birth.

Michael and his band Fitz and the Tantrums were scheduled to perform a concert the night Kaylee went into labor so they had to cancel.

“Hey, San Diego, unfortunately we will not be playing at 91x fest today because FORTUNATELY there is a baby Fitz coming!” the group wrote on its Facebook page. “Thank you so much for understanding. We hope to make it up to you all soon!”